The present invention is directed to the manufacturing of acoustical transducers and, more specifically, to the methods and devices for assembling diaphragms to support frames which are utilized in transducers such as planar magnetic transducers. In accordance with the invention, electrical conductors are applied to the diaphragm material after which the material is conveyed to an applicator station having a bonding and cutting assembly which is operable to secure properly tensioned sections of the diaphragm material to the frames.
Conventionally, planar magnetic speakers or planar magnetic transducers have been manufactured in relatively small volumes for select market applications requiring largely manual assembly processes. Not only is the manual assembly of such transducers inefficient and not cost effective but the operating performance of the end products can not be uniformly maintained. Variation of performance results from a number of factors associated with the assembly procedures including the non-uniform tensioning of transducer diaphragms.
In the field of planar magnetic transducers, it is important that diaphragm responses are uniformly predictable. To optimize performance levels over a wide acoustical range, the tension of the diaphragms and electrical conductors mounted thereon must be maintained within predetermined ranges.
In U.S. Pat. No. 4,803,733 to Carver, the tensioning of a diaphragm of a planar magnetic transducer or speaker is disclosed wherein the diaphragm, having an electrical conductor circuit applied thereto, is initially secured under little or no tension to one half of a diaphragm supporting frame. The frame includes a tensioning groove in which segments of the outer edges of the diaphragm are urged by tensioning members either disposed between opposing frame members or extending from one of the opposing frame members. In U.S. patent application Ser. No. 08/943,272 filed Oct. 3, 1997, now U.S. Pat. No. 5,850,461 in the name of Thomas Zelinka, assigned to the Assignee of the present invention, an improvement over the tensioning groove structure disclosed in the patent to Carver is disclosed which provides for a selective tensioning of diaphragms relative to different portions of the transducer frame such that tensioning may be adjusted and varied across the surface of a diaphragm.
In U.S. Pat. No. 3,939,312, a method of assembling speaker diaphragms is disclosed wherein the diaphragms are applied to frames and thereafter heat is applied to shrink the diaphragms. Unfortunately, with this process, it is necessary to apply heat to the electrical conductors mounted to the diaphragms which can result in damage to the conductors and, further, tensioning by heat shrinkage is not uniform from one diaphragm to another and there is also no control over how the tension may be varied along different axes of the diaphragms.
In view of the foregoing, there is a need to develop processes and machinery for high speed assembly of acoustic diaphragms and support frames in such a manner as to uniformly provide predetermined tensioning of the diaphragms and thus predictable acoustic response to an end product transducer.